1. Field of the Invention
This invention relates to an image reading apparatus and an illuminating apparatus for irradiating transmitting original film on a transparent original table by a transmitting original illuminating unit, and reading an irradiated image by a reading sensor through the transparent original table.
2. Related Background Art
Heretofore, many image reading apparatuses for reading a transmitting original as described in Japanese Patent Application Laid-Open No. 2000-358132 have read an image formed by the imaging lens of a reduction optical system, by the use of a CCD image reading element, and the depth of field of the imaging lens has been deep. Therefore, even if transmitting original film has been more or less far from a transparent original table, the film could be read without any problem, and a film holder for holding down the end portions of the transmitting original film from a vertical direction has been placed on the transparent original table to thereby effect reading. In this case, there has been adopted a construction for illuminating the transmitting original film by the use of a light source contained in a pressure plate, and it has not happened that a plane light source contacts with the transmitting original film. Also, even when use is made of a compact light source as described in Japanese Patent Application Laid-Open No. 2003-008835, no consideration has been given to inadvertent contact of a light source with the depth of transmitting original film.
In recent years, however, with a view to thinning, downsizing and electric power saving of an image reading apparatus, there is an image reading apparatus using an original table contact type reading sensor having a one-to-one magnification imaging lens like a rod lens array. If an attempt is made to mount a transmitting original illuminating unit on such an apparatus to thereby read film, the upper and lower portions of the film cannot be held down by a film holder because the depth of field of the imaging lens is shallow, and thus the film is directly placed on a transparent original table glass. The transmitting original illuminating unit is disposed on it, but when saving the electric power of the image reading apparatus, it is sometimes the case that use is made of a transmitting original illuminating unit using a compact plane light source of a size of the order of one frame of transmitting original film. In this case, if the plane light source portion is not carefully installed so as to be parallel to the film, the corner of the end portion of the transmitting original illuminating unit has sometimes contacted with the film to thereby injure the film.
FIG. 17 of the accompanying drawings schematically shows the construction of a conventional image scanner. The reference numeral 1700 designates the image scanner having a CIS 1702 for scanning along an original glass table 1701 to read film (an original) F placed on the original glass table 1701, and in the CIS 1702, there are disposed a light source member for a reflecting original (not shown), a rod lens array (imaging means) 1703 and a line-shaped photoelectric conversion element 1704. The reference numeral 1705 denotes a film adapter unit (hereinafter referred to as the FAU) comprised of a plane light source member 1706 and a film holder 1707. The plane light source member 1706 has a light source 1709 provided in a plane light source member housing 1708, and a diffusing plate 1710 provided so as to close the underside opening portion of the housing 1708.
When the image of 35 mm photographic film as a transmitting original is to be read, there has further been the following problem. The 35 mm photographic film (hereinafter referred to as the “film F”), as shown in FIG. 16 of the accompanying drawings, has read image areas Fa (dots-and-dash line portions in FIG. 16 of the accompanying drawings) and a non-read image area Fb, and is provided with a plurality of through-holes (hereinafter referred to as the perforations) P located in the non-read image areas Fb and located on the widthwisely opposite sides of the film F and formed in rows in the longitudinal direction of the film F. Feeding gears provided in a camera are engaged with these perforations P so that the film F may be sequentially fed. Here, the spacing between the perforations P on one side in the widthwise direction of the film F and the perforations P on the other side is defined as l.
The read image may sometimes be deteriorated according to such a positional relation between the film F and the line-shaped photoelectric conversion element 1704. The deterioration of the read image will now be described with reference to FIGS. 18 to 23 of the accompanying drawings.
FIG. 18 is a schematic plan view of the image scanner 1700 when the longitudinal direction of the film F and the longitudinal direction of the line-shaped photoelectric conversion element 1704 are made coincident with each other, FIG. 19 is an enlarged view of the film F portion of FIG. 18, FIG. 20 is a cross-sectional view taken along the line 20-20 of FIG. 19, FIG. 21 is a schematic plan view of the image scanner 1700 when the longitudinal direction of the film F and the longitudinal direction of the line-shaped photoelectric conversion element 1704 are made orthogonal to each other, FIG. 22 is an enlarged view of the film F portion of FIG. 21, and FIG. 22 is a cross-sectional view taken along the line 23-23 of FIG. 22.
When the image of the film F is to be read with the longitudinal direction of the film F and the longitudinal direction of the line-shaped photoelectric conversion element 1704 made coincident with each other (when a dots-and-dash line 2500 in FIGS. 18 and 19 is a main scan reading line), light from the light source 1709, as shown in FIG. 20, uniformly passes through the film F including the vicinity of the read image areas Fa to the line-shaped photoelectric conversion element 1704 and therefore, does not adversely affect the image.
However, when the image of the film F is to be read with the longitudinal direction of the film F and the longitudinal direction of the line-shaped photoelectric conversion element 1704 made orthogonal to each other (when a dots-and-dash line 2800 in FIGS. 21 and 22 is a main scan reading line), the light from the light source 1709, as shown in FIG. 23, directly enters from the perforations P in the non-read image area Fb, and diffused light when direct light of a high level enters the rod lens array 1703, etc. arrives at the line-shaped photoelectric conversion element 1704, and as the result, in some cases, it adversely affects the read image near the perforations P.
The line-shaped photoelectric conversion element 1704 has a full length of the order of 220 mm, but is not comprised of a single sensor chip, but is comprised of a plurality of sensor chips of the order of 30 mm-40 mm arranged in a line shape. When the plurality of sensor chips are arranged in a line shape, there is a case where from the problem of assembly accuracy, each sensor chip does not become a straight line in the order of micron, or a case where the pitch of the photoelectric conversion element widens among the chips, so that there is a case where image deterioration called an inter-chip level difference occurs. Therefore, to avoid among the chips and read the above-described film by one chip, there is adopted a construction in which the image of the film F is read with the longitudinal direction of the film F and the longitudinal direction of the line-shaped photoelectric conversion element 1704 made orthogonal to each other, and this leads to the possibility of adversely affecting the read image near the above-described perforations P.